It is standard state of the art practice to provide a scroll housing around wheel fans to increase the efficiency of the fan in providing directional air flow. See for example, Brown, U.S. Pat. No. 3,060,590, Oct. 30, 1962.
The use of scroll housings around wheel fans was so widely accepted that the identical structure was adopted by applicant and others in the construction of surface flow air conveyors. Some examples of patented surface flow air conveyors using scroll-housed wheel fans follows:
__________________________________________________________________________ PATENTS - USA U.S. Pat. No. GRANT DATE: TITLE: __________________________________________________________________________ 3,131,974 May 5, 1964 AIRLIFT CONVEYING OF SOLID OBJECTS 3,180,688 April 27, 1965 AIRLIFT CONVEYING OF SOLIDS 3,267,585 August 23, 1966 CHANGING THE TEMPERATURES OF OBJECTS BY GAS JETS 3,304,619 Feb. 21, 1967 METHOD & MEANS FOR CHANG- ING THE TEMPERATURE OF GRANULAR MATERIALS BY GAS JETS 3,394,463 July 30, 1968 ALTERING THE TEMPERATURE OF GAS CURRENTS 3,418,724 Dec. 31, 1968 METHOD & APPARATUS FOR SUBJECTING MATERIAL TO CONDITIONING GAS WITH WHIRLING MOTION 3,435,536 April 1, 1969 DISCHARGING PARTICULATE MATERIAL FROM STORAGE MEANS, J. W. TINLEY 3,555,693 Jan. 19, 1971 METHOD & APPARATUS FOR TREAT- ING PIECES OF MATERIAL BY MICROWAVE 3,586,382 June 22, 1971 TRANSPORTATION SYSTEM 3,647,266 March 7, 1972 VELOCITY CONTROL SYSTEM FOR AIR CONVEYORS 3,734,567 May 22, 1973 AIR CONVEYOR FOR FLAT THIN ARTICLES 3,890,011 June 17, 1975 SUPPLY OBJECTS FROM AN AIR-FILM CONVEYOR RAPIDLY & INTERMITTENTLY TO A MACHINE 3,980,024 Sept. 14, 1976 AIR PROPELLED VEHICLE TRANSPORTATION SYSTEM 4,078,498 March 14, 1978 SINGLE POWER UNIT AIR PROPELLED SYSTEMS __________________________________________________________________________
Open wheel fans are manufactured by Chicago Blower Corporation and recommended for use in ovens, dryers, and kilns or penthouses in panel walls, ceilings or floors. See Bulletin Sqpf-107, August, 1978. Another manufacturer of open wheel fans, which are also known as plug fans is The New York Blower Company. See undated Bulletin 724-R which suggest that the wheel and inlet cone be mounted within the plenum in special applications. Typical applications shown on Page 20 of the Bulletin indicate the advantages of using plug fans in systems in which air is recirculated within a closed plenum enclosure.
None of the prior art systems known to applicant indicate that an unhoused wheel fan could be used in the construction of surface flow air conveyors.